Measuring increments on boring head

[Bill PhinnParticipant @billphinn90025]

Spoiled by digital readouts on my lathe and milling machine I find it a bit of a culture shock measuring increments on my boring head using only the small non-zeroable dial on the side of it. Backlash in the screw doesn’t help matters.

I’ve thought of using a dial gauge as shown in the picture, but this is susceptible to cosine error and I’ve no spindle lock on my mill either. A new zero obviously has to be taken after every cut as well, not to mention the repositioning of the magnetic stand.

I’ve seen ”solutions” on Youtube of the kind I’m seeking that use a dial gauge or DTI mounted on a spigot held in the boring head’s horizontal tool slot, but this is prone to inaccuracy also if the spigot and gauge have to be removed and reinserted every time.

Any advice on how to get greater accuracy when measuring cuts on the boring head would be greatly appreciated.

 

[bernard towersParticipant @bernardtowers37738]

backlash on your boring head screw is immaterial as you are only travelling in one direction and usually whatever you put on the dial is doubled on the dia. what sort of accuracy are you after? a thou should be achievable. Why not make a shallow plug gauge that is stepped that you can insert after a cut to check where you are.

[Bill PhinnParticipant @billphinn90025]

Thanks for your reply, Bernard.

It’s actually difficult to tell what is backlash and what isn’t on this screw as advancing the screw requires so little effort and the dial can back off (even if the cutter doesn’t) during a cut. The gibs aren’t any looser than they need to be to achieve smooth motion.

Checking dimensions after a cut isn’t a challenge: making sure the cut is what it should be before it’s taken is.

[Howard LewisParticipant @howardlewis46836]

If the clamp screws are lightly nipped, any backlash should be taken out as the cutter is advanced. Once set, the clamp screws should be tightened more, to prevent the cutter backing itself off.

As final size is approached, it will be worth taking one or more spring cuts, without any alteration to the boring head. Check size after each cut if possible.

Howard

[DiogenesParticipant @diogenes]

Yes, it’s advantageous for the adjustment on a (cheap) plain boring head to run with a perceptible bit of ‘drag’.

If your boring head is anything like mine, the fiducial lines provide far better ‘guidance’ than ‘precision’

– I generally employ a similar method to which I use for boring in the lathe, i.e. starting some small way short of finished size, advance your cuts consistently by ‘X division(s)’, and measure after each cut – as you approach final size you should be able to predict & ‘tweak’ your final couple of cuts to take you to the line.

The first couple of times I did this I actually scribbled the numbers down to help keep track..

[John HaineParticipant @johnhaine32865]

I have a small and a large boring head.  The large one was bought from one of the usual suspect suppliers and behaves just as you say.  The only way to make it work is to lock the slide tight for a cut, then bring the adjustment screw hard against the slide  before slacking off the gibs to advance the feed.  Getting a hole the right size is a lottery.

The small one cost a lot more and is an Arrand. Yet again, bought cheap, bought twice.

[Tony Pratt 1Participant @tonypratt1]

Bill Phinn,

I think you are overthinking things, just make sure the back lash is taken out by the first cut.

Tony

[EmgeeParticipant @emgee]

Bill

To make adjusting the boring head simpler and more accurate get one of these Erickson boring heads, each division adds 0.002mm to the diameter, may cost a bit more than others available but you only get what you pay for with tooling. This is a No.12 that uses 12mm diam tools, I also have a No.10 for 10mm tooling.

Emgee

.

 

[JasonBModerator @jasonb]

I find keeping the three screws fairly tight so the adjustment needs a bit of effort on my Soba and Arc ones does not give any backlash as I’m feeding in the same direction. I don’t lock anything for the cut.

Generally I make the hole first as it is easier to make the mating male part fit or if it is something like a bearing I’ll sneak up on the final couple of cuts just 1 increment at a time using the bearing as my “plug gauge”.

[Clive Brown 1Participant @clivebrown1]

The GHT design has a separate lock screw which I find useful. It could be a possible addition to other designs.

[old martParticipant @oldmart]

I also like to keep the adjustment screws fairly tight. I have never tried to accurately measure what the scale markings are, that method with the DTI will have to wait until I next start setting up for boring. I still haven’t got around to making an indexable left handed boring tool for doing external diameters to fit my Soba, the subject of which came up in an earlier thread.

[Bill PhinnParticipant @billphinn90025]

Thanks to everyone for your replies.

I’ve very little experience of using a boring head. I’m sure I’ll get a better feel for adjusting the one I’ve got as my familiarity with it increases. I think I’ll have to scribble the numbers down, as Diogenes suggests, because remembering my starting point and being sure that it is definitely still at my starting point when I begin my next cut has been part of the problem.

Based on several people’s advice, I’m going to experiment with keeping the gib screws a bit tighter on some practice pieces and see how accurately I can hit certain numbers. I may continue to use the dial gauge for a time to see how useful or necessary it turns out to be. I’ve got a set of telescoping gauges to check progress.

My boring head is an “indirect reading boring head” according to this source:

The demonstrator in the video isn’t positioning the dial gauge very carefully in relation to the head, but I think his aim in using it is just to show the difference between direct and indirect reading heads, not to measure increments in use.

The GHT, Arrand and Erickson boring heads look like desirable alternatives to what I have, though they appear to be either hard to find new or a shop-made item (the GHT).

Something like the Seco with its own digital readout would potentially be even better for uninitiated users like me, but no doubt the price reflects their increased convenience: https://www.youtube.com/watch?v=UphtbNkmBcA

In the meantime, the head I’ve got produces very clean cuts indeed, even with its cutter made out of a broken end mill. Once I’ve learned to use it better, I’ll consider whether I deserve and/or need an upgrade.

[duncan webster 1Participant @duncanwebster1]

If you have the gib screws too tight you can get stick/slip where the slide doesn’t move at all until the screw is exerting a decent force, then it moves a lot. The KNH locking screw works well on mine, just remember the last setting on the adjusting dial, or if you’re like me write it down.

[PeteParticipant @pete41194]

It’s a fairly complex to explain question Bill, and there’s always more than one way to do anything. It also took me a very long time just to pick up the information I’ve manged to find and learn a few tricks of my own since it’s not all in any one place that I’ve found.

I’d guess all of these off shore heads were originally cloned from the American made Criterion DBL series of boring heads since they all seem to be the exact same design. And Criterion are pretty specific about only using the center locking screw to lock or unlock the adjustment slide. In fact they now have the other two gib adjustments temporarily covered today because so many won’t read the instructions. https://www.mscdirect.com/product/details/01066489 There’s no need and its actually improper and counter productive to use all three of those gib screws to lock the slide. And most of these cloned heads don’t have a very precise fit with how the collar on the feed screw fits the radial half slot in the head. Properly shimming that for a better and tighter but still a very slight clearance fit might also help. But like others have also said, backlash in the adjustment screw isn’t all that important.

Adjustable slide boring heads have been in common use for roughly 100 years and maybe a bit longer than that. Some were designed and used on jig borers to precision bore holes to under .0001″ /.00254 mm for size, straightness, roundness since at least the late 1920s to early 1930s. However they weren’t priced nor built like some of those Asian boring heads are today. High accuracy screw threads have world wide limit standards for both imperial and metric threads for size, allowable + – for thread flank angles, and much like lead screws on lathes, there accuracy and consistency of pitch. My Criterion heads I believe used finish ground feed screw threads and likely lapped nut threads for both operating smoothness and pitch accuracy. But, there is NO such thing as a perfect thread, Moore Tools in the US tried to produce feed screws and nuts to the accuracy they wanted for there jig borers and grinders. Yet no matter how much time, effort and funding they threw at the problem they failed and mostly due to thread pitch issues. They could and did measure the level of inaccuracy to low millionths of an inch, but they still couldn’t improve or fully eliminate their feed screw and nut inaccuracies. Well before DRO’s were invented, they instead used .0001″ indicators with 1″ travels and what were called high precision distance setting rods that came in sets of 1″ increments for any distance settings beyond the indicators travel limits for the tables X,Y position. Those rods were checked and certified to far better accuracy, but were still a bit like today’s micrometer setting rods. https://www.practicalmachinist.com/forum/threads/jig-bore-measuring-rods-use.428069/#post-4229749

If you want to hit a target dimension with any boring head, it starts with a properly trammed mill, a well built, repeatable, accurate boring and milling head, correct cutting tool angles for the material, and very sharp tools with the correct fine radius on the tool tip. Mill rigidity, spindle grinding, preload and bearing seats quality / accuracy are another big help as well as having built in powered spindle feeds since the holes bored surface finish affects your measurements accuracy as well. With all else being equal, HSS boring bars will usually deflect a fair bit less than carbide tipped, solid carbide will be much less than HSS, but it still depends a lot on the cutting tools shank diameter verses it’s unsupported length. Anything longer than about 3 X the tool diameter for HSS and roughly 5 X diameter for solid carbide might be pushing it a bit. So that depth of cut compensation is then even more important. Highly accurate measurements are just as important as the boring itself. And all of this requires the best methods and techniques you know. Most or maybe all of those cheaper telescoping gauge sets require checking that the telescoping parts are in fact really straight and 100% burr free on all the internal sufaces. If they aren’t, they start to create drag or even bind up, and inaccurate measurements are guaranteed. I own a set of Starrett’s I bought over 40 years ago that have always worked fine out of the box. I also don’t oil mine, instead I use dry graphite. Any oil could become sticky over some time and then start to affect the sensitivity of these types of telescoping gauges. Even then, I doubt I’d bet real money I could guarantee any hole size to much better than maybe .0002″-.0003″ with the metrology equipment I have right now. My mikes can measure and do better than that, but my telescoping gauges can’t. I also find that gently holding the micrometer in a micrometer vise and holding one end of the gauge against the mikes fixed anvil, sweeping the other end of the telescoping gauge past the moving anvil on the micrometer as I’m adjusting it until it just barely starts to drag on the face of that anvil is much more consistent for the measurements repeatable accuracy.

Accurate boring on a lathe or with a boring head in a mill are both the same, you still have to compensate for the inevitable tool and machine deflections. I always use what’s usually thought of as a 3 cut method. To simplify, lets say I’m getting roughly close to size, but my telescoping gauge says I’m exactly .030″ or for metric .9 mm under size. I still want and need that first initial measurement to be accurate, with that baseline, I’d then take 1/3rd or .010″ / .3 mm depth of cut. Then remeasure to see what a lathes boring bar or boring head took for a cut. Lets say it actually took a .009″ /.27 mm depth of cut due to that deflection issue. In either measurement system, that would still leave the hole .021″ /.63 mm under size. For the next cut, I’d probably chose to adjust the lathes cross slide or boring head to take .0105″ / .33 mm depth of cut. Remeasure, now you have a fairly good estimate of how much the tool cuts verses what the adjustment was to hit your last adjustment to very fine limits for the proper adjustment depth of cut. This is simplified with mostly round numbers to make it easier to visualize, but the method is still the same. Subtract the target hole size from your under size measurement, then divide that into 3 very close to equal cuts. If you don’t know the deflection variation of what the tool actually takes verses what you adjusted for, it’s extremely difficult to hit your size. Judging material types and how much experience you have boring to precision sizes are also a big help, and that really isn’t something that imo can be taught. Those spring cuts can help, but in my opinion, there more uncertain just how much they will remove. Multiple passes with roughly the same depth of cut and adjusting for any deflection your then seeing after each cut seems to be more predictable.

The dials on my own Criterion boring heads aren’t adjustable, so for at least the last 3 cuts, I’d do much the same as you do and use a dial indicator. Until I added my mills dro, using that magnetic base and indicator to measure the boring heads adjustment in my opinion took too much time and effort to set it up for measurement as I was adjusting the BH’s slide each time. I then started positioning the indicators base magnetically attached to the table with the indicator tip correctly squared, aligned and zeroed to the boring heads slide. Then I used two 123 blocks bolted down to the mills table, one touching the left side and one touching the rear face of the magnetic base. With those correctly positioned, it’s then fast and easy to slide the base against both of those 123 blocks and magnetically attach the base in the same spot on the mill table each time. Then all you really need to do is fine adjust the indicators zero for the next adjustment.

You do have to watch for any swarf getting into that area if the magnetic base is moved out of the way, but that’s nothing unusual. I always work and visualize much better with imperial measurements, luckily I ran across a fairly good deal for a brand new .0005″ Mitutoyo dial indicator quite a few years ago. So I normally use that as a direct reading method to .001″ for my boring head adjustments and predicted hole size. Although I also have indicators with far finer resolutions and accuracy, however the best only has .003″ of total measurement range. But single point boring isn’t anything as accurate as radial internal grinding would be, and can’t bore finished hole sizes close to that level of accuracy anyway. A .0001″ .002 mm reading indicator might be usable, but you still probably won’t know for sure which .0001″ or thousandth’s of a mm the hole size really is.

There pretty expensive for what they are, but I’ve also found these https://www.starrett.com/products/precision-measuring-tools/precision-hand-tools/fixed-gage-standards/taper-gages are pretty useful to get me fairly close for smaller bored holes that the telescoping gauges can’t do. Finding a very good condition used set in your area might be worthwhile? Holes still need to be properly de-burred before there used since there only a visual gauge. Hopefully all this will save you a bit of time trying to find what I had to over quite a few years.

[Neil LickfoldParticipant @neillickfold44316]

The Vee type indicator holder that fits directly onto the spindle itself, is the best DTI holder for adjusting a boring head. You also want a low force pressure indicator, and remember that every 0.01mm is actually 0.02mm on the bar. Depending on the precision required, you may need a 1 or 2 um indicating dti.

Having the indicator on an external mag base is not a very consistent way of setting a boring head reliably.

Neil

[John Haine]

On John Haine Said:

….Yet again, bought cheap, bought twice.

Only too true!

I never got on with my cheap Soba boring head. The slide, and tool, grubscrews were very poor quality. It was also impossible to bore accurate holes with any sort of consistency due to the sloppy fit of the adjustment screw and slide.

The only solution, for me at least, was to acquire decent boring heads. I now have a Wohlhaupter boring and facing head for the horizontal mill:

And a Kuroda boring and facing head for the vertical mill:

Both of these heads make it simple to bore to a few tenths, which is at the limit of my measurement capability.

The manuals for both the Wohlhaupter and the Kuroda state that the slide locking screw should always be used to lock the slide, except when making adjustments. In the picture of the Kuroda the slide lock is the knurled screw in the centre.

The ideal solution to the original problem is use a quality boring head. It also helps to use home ground HSS toolbits in my experience.

Julie

[bernard towersParticipant @bernardtowers37738]

I second the use of HSS bits they give a far superior finish in all the materials I use IMHO

[Bo’sunParticipant @bosun58570]

Certainly with the generic Boring Heads from the Far East, I second the general idea of keeping the gib screws fairly tight (and locking the slide), but not too tight as to cause stick slip as alluded to earlier.  However for me, the bigger issue is reading the dial and index mark that are slightly recessed into the head with questionable contrast.  I’ve pondered for a while, how to improve the contrast, but that’s still “work in process”.

[PeteParticipant @pete41194]

A couple of very nice B & F heads Julie. I don’t really know anything about those Japanese made Kuroda’s other than I’ve read there very nice. Since your the only one I know of that also owns a Wohlhaupter, how would you compare them?

For the difference between HSS and carbide. I’ve found that the surface finish that can be obtained has everything to do with the quality of the carbide. I bought a set of what Criterion call there stubby boring bars that use braised tips, I suspect there using Micro 100 carbide. How rigid the mill is that there being used in also has a lot to do with it as well. With smaller and lighter mills, HSS probably would be the better choice. I also started with one of those generic $100 boring heads and the almost worthless 9 pc set of carbide tipped boring bars. There’s no comparison at all between how those performed and what I have now, and I certainly don’t miss those frustrations.

[JasonBModerator @jasonb]

With smaller and lighter mills the lathe may actually be the better choice. Unlike the larger machines they are unlikely to have a power feed on the quill and many won’t have a PF on the table so a more consistant feed on the lathe is likely to give a better finish than handfeeding with the quill. The lathe will also do the stepped hole as shown in Julie’s second photo.

I mostly use an insert holder in my heads for parallel cuts, the 9pc sets have mostly been ground for things like external cutting, chamfering or leaving a fillet at the end of the cut.

[Pete]

On Pete Said:

…I don’t really know anything about those Japanese made Kuroda’s other than I’ve read there very nice. Since your the only one I know of that also owns a Wohlhaupter, how would you compare them?

The Wohlhaupter is a UPA4 and the Kuroda is a UPB-3-F. The Kuroda is physically smaller with, naturally, a smaller capability. I don’t have a Kuroda manual, but the Kuroda seems to be identical to a Wohlhaupter UPA3, so a Wohlhaupter UPA3 manual suffices.

To save me typing out the names every time I will abbreviate to W and K.

The W has separate coarse and fine feed screws within the body and these work very well (see below). The K uses a ring on the top of the head. The same ring is used for both coarse and fine feed, with a button that is pushed to engage a reduction gear for fine feed. On balance I prefer the W method, although the scale on the K is easier to read.

Slide locking on the W is via a hex grub screw while on the K it is a knurled knob. I prefer the K method as it saves looking for the Allen key every time.

The biggest difference is on feeds for facing and grooving. The K has one feed rate of 0.002″ per rev. The W has 12 buttons, each of which creates an incremental feed of 0.0008″ per rev. So the total feedrate can range from 0.0008″ to 0.0096″ per rev. The facing feed automatic stop on both heads is very similar.

When I first used the W for boring the cylinders on my model engines I had all sorts of trouble getting the fine feed to work. Movement seemed to be random and I resorted to using a dial indicator on the body. After consulting others it turned out that the W had a couple of simple parts missing that locked the coarse feed and enabled the fine feed. So I stripped and cleaned the head:

And designed and made the missing parts. Once done everything worked so much better and putting on a cut of, say 1 thou, was easy and was exactly one thou.

The K worked properly straight out of the box.

In summary both heads work extremely well, the W is more capable but this is mainly due to being a bigger head.

Julie

[PeteParticipant @pete41194]

Many thanks for those extra details about each different head Julie.

I looked for a long time for one of the smaller Wohlhaupters without much success for condition, possible unknown internal damage and price. Since Wohlhaupter isn’t manufacturing them any more, used is the only option as you’d already know. I thought there were just too many unknowns without being able to try anything I was interested in first. So I finally bought a Narex VHU-36 B&F kit from MSC during a sale. If your interested, page 9 of this PDF has the operating instructions, and the parts exploded view on page 20. https://www.narexmte.cz/servis/Vhu_Instructions_complet_EN.pdf

My Bridgeport clone only has an R8 taper, so I felt anything larger than what I bought would be just too much. Things would be different if I also had a larger horizontal mill like yours with what looks to be a 40 taper, so what you bought for it seems to be a very good choice. And very smart to lay out and list the part numbers during that disassembly.

I really like the simple but well thought out design Narex uses for there replaceable tool shank attachment, but converted over to your UK pounds, even a R8 shank runs about 350 BP’s today. And so far I’ve never found any other company that produces them. I think there there tool shanks are completely over priced for what they are. And the heads have almost doubled in price since I bought mine. But they might be better in the UK than here. Since mine is the only B&F head I’ve ever used, I can’t compare how good it is to anything else, but it seems to have been really well designed, built and finish ground since there’s no detectable clearances at all.

[Julie AnnParticipant @julieann]

If the Kuroda head hadn’t come up for sale I was looking at a clone version from Arc, which might have been Narex. Just tried looking and can’t find it on the Arc website, so they may not sell it any more. If I recall is was over £500 so probably not a big seller.

Julie

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